When your space is at a premium

In pick-and-place operations, space is often a valuable commodity at the end of an end effector. If there isn't enough space to mount sensors directly on a gripper or other end effector, designers are forced to find a creative alternative. One such alternative is the new magnetoinductive BIL analog absolute linear position sensor, from Balluff Inc., Florence, Ky. The BIL sensor provides accurate, non-contact continuous position feedback of miniature grippers. Miniaturized for sensing motion of short strokes, the MicroBIL provides a linear output signal that is proportional to the position of pneumatic miniature grippers equipped with mounting T-slots. Continuous output of the MicroBIL's signal allows absolute real-time sensing of gripper jaw endoftravel as well as continuous absolute feedback of intermediate positions.

Compact and flexibleMicroBIL consists of a tiny 5- ×3.15- ×39-mm magnetoinductive sensor head connected via cable to a small electronics module that processes the signal from the sensor and produces voltage or current output. As shown in the photo, the electronics module is larger than the sensor head, but it can be mounted elsewhere on a machine, where space is less critical.

The sensor head detects the position of a small magnet embedded in a piston of a pneumatic cylinder in the gripper. The magnet normally would be used to actuate discrete on-off Hall-effect sensors that simply indicate when a gripper has opened or closed. The piston moves perpendicular to the motion of the grippers, which are actuated by the piston through a mechanical linkage. Because the gripper housing is aluminum, the magnetic field of the piston passes through it.

The MicroBIL delivers high resolution, analog temperaturecompensated linearized stroke information to 10 mm. The Micro-BIL has no moving parts other than a magnet within its electronics module. Its sensor head and processing elements are sealed to IP 67, providing high resistance to shock, vibration, moisture, and common contaminants.

" Balluff magnetoinductive technology involves interaction between a magnet attached to the piston and a specially shaped triangular coil," states Balluff linear feedback product manager, Henry Menke. "The BIL is a cost-effective upgrade from conventional continuous position feedback sensing devices on virtually any short displacement motion-based system. It also adds real flexibility to on-off, end-of-stroke systems, and with its small size, you can mount it just about anywhere."

Menke says the continuous feedback from the sensor allows the gripper be used as a measuring device. Or, by comparing sensor output to a predetermined signal, the sensor could verify that a correct part was grasped or that it was in the proper orientation.

For more information on Balluff's MicroBIL sensor, call (800) 543-8390 or visit www.balluff.com.